A diluent is used to reduce the viscosity of the recovered bitumen from oil sands. The viscosity must be reduced to make it possible to remove the residual impurities like water and fine minerals from the bitumen.
The diluent that is used is mixed with the recovered bitumen, at a certain ratio with the bitumen, to arrive at a workable viscosity of the diluted bitumen.
When the impurities are removed, as for example by centrifugation, a certain percentage of the original diluent is lost along with the water and fine solids.
The present methods of stripping the diluents from the tailing stream is to use vacuum distillation with overhead vapour recovery. These methods are only partially successful in recovering the diluent. This results in substantial economic loss.
The present invention provides a method and apparatus for diluent recovery from extraction tailings that is more effective than existing procedures.
According to one aspect of the invention streams of extraction tailings Are directed through a nozzle at an impaction target. Next, saturated steam is injected into the stream of extraction tailings to produce a confluent stream of steam and extraction tailings. Rapid expansion of the steam causes acceleration of the composite stream resulting in a violent collision with the impaction target. The expanding steam dramatically increases the impact velocity. By utilizing this technique impact velocities approaching 7,000 feet per minute can be achieved. It is preferred to use a plurality of nozzles positioned in a common horizontal plane with a stream of one of the nozzles serving as the impaction target for the other of the nozzles. A preferred configuration is to position two nozzles in 180 degree opposed orientation.
Utilizing the above principles of operation there is provided an apparatus for diluent recovery which is comprised of a containment vessel having a top, a bottom, and peripheral side walls. A plurality of inlet nozzles are secured in a common horizontal plane to the peripheral side walls. Each nozzle has a first inlet for receiving a first fluid, a second inlet for receiving a second fluid and a single outlet for discharging a mixed stream of the first and second fluids. The mixed discharge stream of one of the nozzles is focused at the mixed discharge stream of the other of the nozzles, such that the mixed discharge streams impact each other. Means is provided positioned adjacent the top of the containment vessel for drawing off the vapors resulting from the impact. An outlet is positioned adjacent the bottom of the containment vessel for removing extraction tailings which have been stripped of diluent.
Although there are a variety of configurations that can be used in terms of the number of nozzles, it is preferred to use two nozzles oriented in a common plane disposed in confronting relation 180 degrees apart.
While there are a variety of nozzles that are capable of handling a mixed stream of steam and extraction tailings, it is preferred that the nozzle enhance the accelerating effect of the rapidly expanding steam. Even more beneficial results may be obtained when each nozzle includes a body having a passage leading to the outlet and the first inlet has an extension portion disposed in the passage. A steam chamber communicates with the first inlet and circumscribes the second inlet. The steam chamber has a short spiral that surrounds the second inlet, imparting to the steam flow a spiraling motion at the outlet of the nozzle. The rotating and accelerating steam flow will tend further to increase the intensity of the impact when the opposing jets meet.